1. Field of the Invention
The invention concerns a method and an apparatus for automatically processing whole flat fish which include a head, a tail, a body comprising a ventral cavity containing internal organs and defining a ventral and a dorsal edge with ventral and dorsal edge fins extending from the interhemal and interneural spines, respectively, which are imbedded in strips of fatty tissue, wherein the flat fish are conveyed in their longitudinal direction, image data is generated, processed in a controller and then utilized to control at least one cutting apparatus.
2. Prior Art
In general, flat fish fillets are automatically obtained from the fish by means of conventional filletting cuts performed after first removing the head of the fish together with the internal organs and, in some cases, the tail as well.
Particularly efficient flat fish filletting apparatus of this kind are comprised in two machines manufactured by Nordischer Maschinenbau Rud. Baader GmbH & Co. KG, Lubeck, Germany ("Baader"), the Baader 175 and Baader 176 machines, which are described in patents U.S. Pat. No. 3,964,132 and U.S. Pat. No. 5,088,958, respectively. The fillets obtained by these apparatus are free of fins, as the fillets are sliced away from the skeleton in such a way that the dorsal, ventral and anal fins located around the fish edges remain attached to the skeleton.
However, the resulting fillets also have strips of often strongly flavoured fatty tissue, which are characteristic of flat fish attached to their outer edges. These strips of fatty tissue are unacceptable in some consumer markets due to their flavour and have to be removed from the fillets after processing.
This is generally performed by hand, which requires a large number of trimming personnel and results in a considerable increase in cost.
In an attempt to reduce this cost, the document EP 0 272 708 proposes the automated removal of these strips wherein fillets obtained with the conventional filletting apparatus are first skinned and then removed of the fat strips by rotating brushes which brush the fat strip away from the fillet. However, the removal of the fatty tissue with this apparatus has proved unreliable so that the resulting product is rarely satisfactory. In addition, this procedure has an undesirable side-effect to the extent that the processed fillets have a roughened surface as a result of the brushing tools coming into contact with and damaging the fillet surface.
Other apparatus have been developed for pre-processing flat fish to remove the fins prior to a filletting step. An example of such apparatus is disclosed in EP 0 459 558. This apparatus works with an x-ray imaging device which generates a skeleton image of the fish and sends this image data to a processor. The computer controls a water-jet cutting apparatus comprising two cutting nozzles and arranged over the path of the advanced fish in response to the image data. In this manner, the head and the ventral cavity containing the internal organs, the anal and dorsal fins and the tail fin may be removed from the fish body in one cutting process, which may subsequently be filletted.
However this apparatus is very bulky and costly as a result of both the x-ray device and the high pressure water source. Moreover, the employment of these two potentially hazardous units necessitates the observance of costly and complex measures to safeguard operator safety in accordance with safety regulations.
A further apparatus of this kind is disclosed in U.S. Pat. No. 5,378, 194 (Hjorth) in which the fish is advanced tail first through a measuring station which determines the fish length and the resulting length measurement is used to select a predetermined programme, which controls the transverse movement of a pair of circular knives with respect to the fish to cut off the fins. The programme controls the knives to describe a curve which is based on the statistically determined approximate relation between the fish length and the fish outer contour. The apparatus further comprises a cutting apparatus for removing the head with the ventral cavity and the tail. This device is activated after the fins have been removed, so that a fin-free fish body is obtained, which may subsequently be filletted in the usual manner.
This patent specifically deals with cutting off the dorsal and anal fins and mentions the problems associated with the removal of the fins, but not the strips of fatty tissue lying inside the fins. As a result, a large number of trimming personnel are required to tidy up the fillets and remove the remaining pieces of fatty tissue from the fillets.
Prohibitively high trimming costs are thus associated with high-yield production of fillets processed with this apparatus.